Numerical modeling of groundwater and air flow between compacted bentonite and fractured crystalline rock

The geological repository for final storage of spent nuclear fuel, envisioned by the Swedish Nuclear Fuel and Management Company (SKB), relies on several barriers: copper canisters deposited in holes in the floor of underground tunnels in deep bedrock, embedded in a buffer of compacted bentonite. The initially unsaturated buffer would take up water from the surrounding rock mass and swell to seal any potential gap. This initial two-phase (gas and liquid) regime with two components (air and water) may impact the final density, swelling pressure and biogeochemical conditions in the buffer. A main objective of this work is to identify factors and mechanisms that govern deposition hole inflow and bentonite wetting under the prevailing two-phase flow conditions in sparsely fractured bedrock. For this purpose, we use the numerical code TOUGH2 to perform two-phase flow simulations, conditioned by a companion field experiment (the Bentonite Rock Interaction Experiment or BRIE) performed in a 417 m deep tunnel of the Äspö Hard Rock Laboratory in southeastern Sweden. The models predict a significant de-saturation of the rock wall, which was confirmed by field data. To predict the early buffer wetting rates and patterns, the position of local flowing fractures and estimates of local rock matrix permeability appear more important than the total open hole groundwater inflow. A global sensitivity analysis showed that the buffer wetting time and the persistence of unsaturated conditions over extended periods of time in the rock depend primarily on the local fracture positions, rock matrix permeability, ventilation conditions in the tunnel and pressure far in the rock. Dismantling photographs from BRIE were used to reconstruct a fine-scale snapshot of saturation at the bentonite/rock interface, showing tremendous spatial variability. The high level of heterogeneity in the rock generates complex two-phase flow phenomena (air trapping, dissolution), which need to be accounted for in buffer design and rock suitability criteria. In particular, results suggest that uncertainties regarding two-phase flow behavior are relatively high close to residual air saturation, which may also have important implications for other applications involving two-phase flows, such as geological storage of carbon dioxide.At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Manuscript. Paper 4: Manuscript.</p

Dynamics of internal nutrient sources in the Baltic Sea - A comparative modelling study of the Gulf of Finland.

For decades the Baltic Sea has been subject to eutrophication due to heavy anthropogenic nutrient loads on the aquatic ecosystem. Quantitative projections of its effects require an understanding of its driving mechanisms, i.e., the hydrodynamics that are responsible for the physical transport and mixing and the biogeochemical nutrients pathways within the algal ecosystem and between the particulate and dissolved phases in the water and in the sediments. A simple basin-scale hydrodynamic framework is set for the Gulf of Finland to test different descriptions of the biogeochemical transformations and determine the most robust modelling strategy. A recently developed criterion to determine the occurrence of anoxic events, based on the amount of fresh carbon detritus in the sediments is implemented in comparison with the classical criterion based on the oxygen concentration in the bottom water. Time-averaging of the hydrodynamics over larger than daily intervals is proved to hinder the capture of rapid mixing events jeopardizing irremediably the water quality simulation. The new carbon based criterion for anoxia shows a better dynamic response and is less sensitive to the model’s internal parameters. An internal source in the sediments correlated to the amount of fresh detritus, to represent the release of iron-bound phosphorus is confirmed as a versatile modelling assumption

Initiation of motor responses in developing Xenopus Laevis tadpoles

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Land reflection seismic, hydrogeological and magnetic study of an area prone to quick-clay landslides in southwest Sweden

Quick-clay landslides are common geohazards in Nordic countries and Canada. The presence of potential quick clays is confirmed using geotechnical investigations, but near-surface geophysical methods, such as seismic and resistivity surveys, can also help identifying coarse-grained materials associated to the development of quick clays. We present the results of four reflection seismic profiles next to the Göta River in Sweden, along which many quick-clay landslide scars exist. An extensive coarse-grained layer exists in the sedimentary sequence and is interpreted and modeled in a regional context. Hydrological modeling of the coarse-grained layer is performed. Magnetic data are also studied within this investigation. Four reflection seismic profiles collected in 2013 (line 5 has two parts, cabled geophones and wireless stations).Jordskred av snabblera är vanliga "geohazards" i Norden och Kanada. Närvaron av potentiella snabbleror bekräftas med hjälp av geotekniska undersökningar, men geofysiska metoder i närheten av ytan, såsom seismiska och resistivitetsundersökningar, kan också bidra till att identifiera grovkornigt material i samband med utvecklingen av snabba leror. Vi presenterar resultaten av fyra reflexions-seismiska profiler bredvid Göta-floden i Sverige, längs vilka många jordskred av snabblera finns. Ett omfattande grovkornigt lager finns i sedimentärsekvensen och tolkas och modelleras i ett regionalt sammanhang. Hydrologisk modellering av det grovkorniga skiktet utförs. Magnetiska data studeras också inom denna undersökning

Land reflection seismic, hydrogeological and magnetic study of an area prone to quick-clay landslides in southwest Sweden - Hydrogeological modeling of an area prone to quick-clay landslides in southwest Sweden

Quick-clay landslides are common geohazards in Nordic countries and Canada. The presence of potential quick clays is confirmed using geotechnical investigations, but near-surface geophysical methods, such as seismic and resistivity surveys, can also help identifying coarse-grained materials associated to the development of quick clays. We present the results of four reflection seismic profiles next to the Göta River in Sweden, along which many quick-clay landslide scars exist. An extensive coarse-grained layer exists in the sedimentary sequence and is interpreted and modeled in a regional context. Hydrological modeling of the coarse-grained layer is performed. Magnetic data are also studied within this investigation.Jordskred av snabblera är vanliga "geohazards" i Norden och Kanada. Närvaron av potentiella snabbleror bekräftas med hjälp av geotekniska undersökningar, men geofysiska metoder i närheten av ytan, såsom seismiska och resistivitetsundersökningar, kan också bidra till att identifiera grovkornigt material i samband med utvecklingen av snabba leror. Vi presenterar resultaten av fyra reflexions-seismiska profiler bredvid Göta-floden i Sverige, längs vilka många jordskred av snabblera finns. Ett omfattande grovkornigt lager finns i sedimentärsekvensen och tolkas och modelleras i ett regionalt sammanhang. Hydrologisk modellering av det grovkorniga skiktet utförs. Magnetiska data studeras också inom denna undersökning

Land reflection seismic, hydrogeological and magnetic study of an area prone to quick-clay landslides in southwest Sweden - Modeled subsurface interfaces of an area prone to quick-clay landslides in southwest Sweden

Quick-clay landslides are common geohazards in Nordic countries and Canada. The presence of potential quick clays is confirmed using geotechnical investigations, but near-surface geophysical methods, such as seismic and resistivity surveys, can also help identifying coarse-grained materials associated to the development of quick clays. We present the results of four reflection seismic profiles next to the Göta River in Sweden, along which many quick-clay landslide scars exist. An extensive coarse-grained layer exists in the sedimentary sequence and is interpreted and modeled in a regional context. Hydrological modeling of the coarse-grained layer is performed. Magnetic data are also studied within this investigation. Modeled interfaces (xyz).Jordskred av snabblera är vanliga "geohazards" i Norden och Kanada. Närvaron av potentiella snabbleror bekräftas med hjälp av geotekniska undersökningar, men geofysiska metoder i närheten av ytan, såsom seismiska och resistivitetsundersökningar, kan också bidra till att identifiera grovkornigt material i samband med utvecklingen av snabba leror. Vi presenterar resultaten av fyra reflexions-seismiska profiler bredvid Göta-floden i Sverige, längs vilka många jordskred av snabblera finns. Ett omfattande grovkornigt lager finns i sedimentärsekvensen och tolkas och modelleras i ett regionalt sammanhang. Hydrologisk modellering av det grovkorniga skiktet utförs. Magnetiska data studeras också inom denna undersökning

Land reflection seismic, hydrogeological and magnetic study of an area prone to quick-clay landslides in southwest Sweden

Quick-clay landslides are common geohazards in Nordic countries and Canada. The presence of potential quick clays is confirmed using geotechnical investigations, but near-surface geophysical methods, such as seismic and resistivity surveys, can also help identifying coarse-grained materials associated to the development of quick clays. We present the results of four reflection seismic profiles next to the Göta River in Sweden, along which many quick-clay landslide scars exist. An extensive coarse-grained layer exists in the sedimentary sequence and is interpreted and modeled in a regional context. Hydrological modeling of the coarse-grained layer is performed. Magnetic data are also studied within this investigation.Jordskred av snabblera är vanliga "geohazards" i Norden och Kanada. Närvaron av potentiella snabbleror bekräftas med hjälp av geotekniska undersökningar, men geofysiska metoder i närheten av ytan, såsom seismiska och resistivitetsundersökningar, kan också bidra till att identifiera grovkornigt material i samband med utvecklingen av snabba leror. Vi presenterar resultaten av fyra reflexions-seismiska profiler bredvid Göta-floden i Sverige, längs vilka många jordskred av snabblera finns. Ett omfattande grovkornigt lager finns i sedimentärsekvensen och tolkas och modelleras i ett regionalt sammanhang. Hydrologisk modellering av det grovkorniga skiktet utförs. Magnetiska data studeras också inom denna undersökning

Subsurface Characterization of a Quick-Clay Vulnerable Area Using Near-Surface Geophysics and Hydrological Modelling

Quick-clay landslides are common geohazards in Nordic countries and Canada. The presence of potential quick clays is confirmed using geotechnical investigations, but near-surface geophysical methods, such as seismic and resistivity surveys, can also help identify coarse-grained materials associated with the development of quick clays. We present the results of reflection seismic investigations on land and in part of the Göta River in Sweden, along which many quick-clay landslide scars exist. This is the first time that such a large-scale reflection seismic investigation has been carried out to study the subsurface structures associated with quick-clay landslides. The results also show a reasonable correlation with radio magnetotelluric and travel-time tomography models of the subsurface. Other ground geophysical data, such as high magnetic values, suggest a positive correlation with an increased thickness of the coarse-grained layer and shallower depths to the top of the bedrock and the top of the coarse-grained layer. The morphology of the river bottom and riverbanks, e.g. subaquatic landslide deposits, is shown by side-scan sonar and bathymetric data. Undulating bedrock, covered by subhorizontal sedimentary glacial and postglacial deposits, is clearly revealed. An extensive coarse-grained layer (P-wave velocity mostly between 1500 and 2500 ms-1 and resistivity from approximately 80 to 100 Ωm) exists within the sediments and is interpreted and modelled in a regional context. Several fracture zones are identified within the bedrock. Hydrological modelling of the coarse-grained layer confirms its potential for transporting fresh water infiltrated in fractures and nearby outcrops located in the central part of the study area. The modelled groundwater flow in this layer promotes the leaching of marine salts from the overlying clays by seasonal inflow–outflow cycles and/or diffusion, which contributes to the formation of potential quick clays